Dispersant-viscosity improvers for lubricating oil compositions

ABSTRACT

Graft copolymers useful as a dispersant-viscosity improver for lubricating oil compositions comprise a hydrocarbon polymer having graft polymerized thereon at least two nitrogen containing units, at least one of the nitrogen containing units being derived from at least one of a neutral N-(lower hydrocarbyl group)- (meth)acrylamide and a neutral N,N-di-(lower hydrocarbyl group)- (meth)acrylamide, wherein the total number of carbon atoms in the lower hydrocarbyl groups does not exceed 9, and at least one of the nitrogen containing units being derived from at least one vinylic nitrogen containing heterocyclic compound.

This application is a 371 of PCT/6500/25173 Sep. 14, 2000.

FIELD OF THE INVENTION

This invention relates to dispersant-viscosity improvers for lubricatingoils, and oil compositions and concentrates containing suchdispersant-viscosity improvers.

BACKGROUND OF THE INVENTION

The viscosity of lubricating oils, particularly the viscosity of mineraloil based lubricating oils, is generally dependent upon temperature. Asthe temperature of the oil is increased, the viscosity decreases at anundesirable rate.

The function of a viscosity improver is to reduce the extent of thedecrease in viscosity as the temperature is raised or to reduce theextent of the increase in viscosity as the temperature is lowered, orboth. Thus, a viscosity improver ameliorates the change of viscosity ofan oil containing it with changes in temperature. The fluiditycharacteristics of the oil are improved.

Viscosity improvers are usually polymeric materials and are oftenreferred to as viscosity index improvers or as viscosity modifiers.

Dispersants are also well-known in the lubricating art. Dispersants areemployed in lubricants to keep impurities, particularly those formedduring operation of mechanical devices such as internal combustionengines, automatic transmissions, etc. in suspension rather thanallowing them to deposit as sludge or other deposits on the surfaces oflubricated parts.

Multifunctional additives that provide both viscosity improvingproperties and dispersant properties are likewise known in the art. Suchproducts are described in numerous publications including DieterKlamann, “Lubricants and Related Products”, Verlag Chemie Gmbh (1984),pp 185-193; C. V. Smalheer and R. K. Smith “Lubricant Additives”,Lezius-Hiles Co. (1967); M. W. Ranney, “Lubricant Additives”, Noyes DataCorp. (1973), pp 92-145, M. W. Ranney, “Lubricant Additives, RecentDevelopments”, Noyes Data Corp. (1978), pp 139-164; and M. W. Ranney,“Synthetic Oils and Additives for Lubricants”, Noyes Data Corp. (1980),pp 96-166. Each of these publications is hereby expressly incorporatedherein by reference.

Dispersant-viscosity improvers are generally prepared byfunctionalizing, i.e., adding polar groups to, a hydrocarbon polymerbackbone.

Hayashi, et al, U.S. Pat. No. 4,670,173 relates to compositions suitablefor use as dispersant-viscosity improvers made by reacting an acylatingreaction product which is formed by reacting a hydrogenated blockcopolymer and an alpha-beta olefinically unsaturated reagent in thepresence of free-radical initiators, then reacting the acylating productwith a primary amine and optionally with a polyamine and amono-functional acid.

Chung et al, U.S. Pat. No. 5,035,821 relates to viscosity indeximprover-dispersants comprised of the reaction products of an ethylenecopolymer grafted with ethylenically unsaturated carboxylic acidmoieties, a polyamine having two or more primary amino groups or polyoland a high functionality long chain hydrocarbyl substituted dicarboxylicacid or anhydride.

Van Zon et al, U.S. Pat. No. 5,049,294, relates to dispersant/VIimprovers produced by reacting an a alpha-beta unsaturated carboxylicacid with a selectively hydrogenated star-shaped polymer then reactingthe product so formed with a long chain alkane-substituted carboxylicacid and with a C₁ to C₁₈ amine containing 1 to 8 nitrogen atoms and/orwith an alkane polyol having at least two hydroxy groups or with thepreformed product thereof.

Bloch et al, U.S. Pat. No. 4,517,104, relates to oil soluble viscosityimproving ethylene copolymers reacted or grafted with ethylenicallyunsaturated carboxylic acid moieties then with polyamines having two ormore primary amine groups and a carboxylic acid component or thepreformed reaction product thereof.

Gutierrez et al, U.S. Pat. No. 4,632,769, describes oil-solubleviscosity improving ethylene copolymers reacted or grafted withethylenically unsaturated carboxylic acid moieties and reacted withpolyamines having two or more primary amine groups and a C₂₂ to C₂₈olefin carboxylic acid component.

Steckel, U.S. Pat. No. 5,160,648 describes dispersant materials preparedby reacting highly condensed polyamines with carboxylic reactants andphenolic reactants.

Stambaugh et al, U.S. Pat. No. 4,146,489 relates to graft copolymerswherein the backbone polymer is a rubbery, oil solubleethylene-propylene copolymer or ethylene-propylene diene modifiedterpolymer and the graft monomer is a C-vinyl pyridine orN-vinylpyrrolidone. They are described as providing dispersantproperties to hydrocarbon fuels and combined viscosity index improvementand dispersant properties to lubricating oils for internal combustionengines. The graft copolymers are prepared by intimate admixture ofbackbone polymer, graft monomer and free radical initiator at atemperature below initiation temperature, followed by a temperatureincrease to or above initiation temperature.

Jost et al, U.S. Pat. No. 4,338,418 discloses a method of making alubricating-oil additive which improves the viscosity index and has adispersing and detergent action, which method comprises graftcopolymerizing, onto an oil-soluble base polymer, from 0.5 to 10 partsof a polymerizable lactam together with 0.1 to 3 parts of apolymerizable N-heterocyclic compound, said parts being by weight ofsaid base polymer, and the lubricating oil additives so produced.

Each of these patents is hereby expressly incorporated herein byreference.

For additional disclosures concerning multi-purpose additives andparticularly viscosity improvers and dispersants, the disclosures of thefollowing United States patents are incorporated herein by reference:

2,973,344 3,488,049 3,799,877 3,278,550 3,513,095 3,842,010 3,311,5583,563,960 3,864,098 3,312,619 3,598,738 3,864,268 3,326,804 3,615,2883,879,304 3,403,011 3,637,610 4,033,889 3,404,091 3,652,239 4,051,0483,445,389 3,687,849 4,234,435

As noted above, dispersant viscosity improvers have been prepared viafree radical grafting of vinyl nitrogen monomers onto a wide variety ofhydrocarbon polymer backbones. Some vinyl nitrogen monomers such asN-vinyl pyrrolidone and dimethylaminoalkyl methacrylamides are usuallyeasily grafted under free radical conditions. Other vinyl nitrogenmonomers such as N-vinyl imidazole tend to resist grafting under freeradical conditions.

It has now been found that simultaneous grafting of certain specific andwell-defined combinations of two or more different nitrogenous vinylmonomers leads to more efficient grafting, especially of monomers thatare difficult to graft employing more conventional techniques. Moreover,the graft copolymers obtained thereby demonstrate surprisinglyoutstanding dispersancy and sludge suspension properties.

It is a primary object of this invention to provide novel multi-purposelubricant additives.

A more specific object is to provide multi-purpose additives directed toimproving lubricant viscosities and dispersancy properties.

A further object is to provide processes for preparing suchmulti-purpose additives.

Another object is to facilitate grafting, under free radical conditions.of vinylic nitrogen containing monomers onto a hydrocarbon backbone.

Still another object is to provide lubricants having improveddispersancy and viscosity properties.

Other objects will in part be obvious in view of this disclosure andwill in part appear hereinafter.

SUMMARY OF THE INVENTION

The present invention is directed to a graft copolymer useful as adispersant-viscosity improver for lubricating oil compositions. Thegraft copolymer comprises a hydrocarbon polymer having graft polymerizedthereon at least two nitrogen containing units, at least one of thenitrogen containing units being derived from at least one of a neutralN-(lower hydrocarbyl group)- (meth)acrylamide and a neutralN,N-di-(lower hydrocarbyl group)- (meth)acrylamide, wherein the totalnumber of carbon atoms in the lower hydrocarbyl groups does not exceed9, and at least one of the nitrogen containing units being derived fromat least one vinylic nitrogen containing heterocyclic compound.

This invention is also directed to a process for preparing the graftcopolymer, methods for improving the efficiency of free radical graftingof vinylic nitrogen containing heterocyclic monomers onto hydrocarbonpolymers, additive concentrates and lubricating oil compositionscomprising the copolymers of the invention, and methods for improvingthe viscometrics and dispersancy characteristics of lubricating oilcompositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, a composition of matter suitable foruse as a dispersant-viscosity improver for lubricating oil compositionsis a graft copolymer comprising a hydrocarbon polymer having graftpolymerized thereon at least two different nitrogen containing units, atleast one of the nitrogen containing units being derived from at leastone of a neutral N-(lower hydrocarbyl group)- (meth)acrylamide and aneutral N,N-di-(lower hydrocarbyl group)- (meth)acrylamide, wherein thetotal number of carbon atoms in the lower hydrocarbyl groups does notexceed 9, and at least one of the nitrogen containing units beingderived from at least one vinylic nitrogen containing heterocycliccompound.

As used herein, graft copolymers are defined as copolymers having apolymeric hydrocarbon backbone chain to which groups of a differentchemical composition are attached at one or more positions along thebackbone. The attached groups may be monomeric or polymeric, oftenoligomeric. The graft copolymers of this invention have uniqueproperties resulting from the combination of the grafted units togetherwith the backbone polymer. The use of the mixture of graft monomers alsofacilitates the grafting process.

As used herein, the terms “hydrocarbon”, “hydrocarbyl” or “hydrocarbonbased” mean that the group being described has predominantly hydrocarboncharacter within the context of this invention. These include groupsthat are purely hydrocarbon in nature, that is, they contain only carbonand hydrogen. They may also include groups containing substituents oratoms which do not alter the predominantly hydrocarbon character of thegroup. Such substituents may include halo-, alkoxy-, nitro-, etc. Thesegroups also may contain hetero atoms. Suitable hetero atoms will beapparent to those skilled in the art and include, for example, sulfur,nitrogen and oxygen. Therefore, while remaining predominantlyhydrocarbon in character within the context of this invention, thesegroups may contain atoms other than carbon present in a chain or ringotherwise composed of carbon atoms.

In general, no more than about three non-hydrocarbon substituents orhetero atoms, and preferably no more than one, will be present for every10 carbon atoms in the hydrocarbon or hydrocarbon based groups. Mostpreferably, the groups are purely hydrocarbon in nature, that is theyare essentially free of atoms other than carbon and hydrogen.

Throughout the specification and claims the expression oil soluble ordispersible is used. By oil soluble or dispersible is meant that anamount needed to provide the desired level of activity or performancecan be incorporated by being dissolved, dispersed or suspended in an oilof lubricating viscosity. Usually, this means that at least about 0.001%by weight of the material can be incorporated, in a lubricating oilcomposition. For a further discussion of the terms oil soluble anddispersible, particularly “stably dispersible”, see U.S. Pat. No.4,320,019 which is expressly incorporated herein by reference forrelevant teachings in this regard.

The Hydrocarbon Polymer

As used herein, the expression ‘polymer’ refers to polymers of alltypes, i.e., homopolymers and copolymers. The term homopolymer refers topolymers derived from essentially one monomeric species; copolymers aredefined herein as being derived from 2 or more monomeric species.

The hydrocarbon polymer is an essentially hydrocarbon based polymer,usually one having a number average molecular weight ({overscore(M)}_(n)) ranging from about 6,000, often from about, 20,000 and up toabout 500,000, often up to about 300,000 more often up to about 200,000.Molecular weights of the polymeric hydrocarbon polymer are determinedusing well known methods described in the literature. Examples ofprocedures for determining the molecular weights are gel permeationchromatography (GPC) (also known as size-exclusion chromatography) andvapor phase osmometry (VPO). These and other procedures are described innumerous publications including:

P. J. Flory, “Principles of Polymer Chemistry”, Cornell University Press(1953), Chapter VII, pp 266-316, and

“Macromolecules, an Introduction to Polymer Science”, F. A. Bovey and F.H. Winslow, Editors, Academic Press (1979), pp 296-312.

W. W. Yau, J. J. Kirkland and D. D. Bly, “Modem Size Exclusion LiquidChromatography”, John Wiley and Sons, New York, 1979.

These publications are hereby incorporated by reference for relevantdisclosures contained therein relating to the determination of molecularweight.

A measurement which is complementary to, and often descriptive of, apolymer's molecular weight is the melt index (ASTM D-1238)which is ameasure of the relative flow or fluidity of a polymer under definedconditions of pressure and temperature. Polymers of low melt indexgenerally have a high molecular weight and/or a high degree oflinearity, and vice versa. The grafted polymers of the present inventionpreferably have a melt index of up to 20 dg/min, more preferably 0.1 to10 dg/min.

When the molecular weight of a polymer is greater than desired, it maybe reduced by techniques known in the art. Such techniques includemechanical shearing of the polymer employing masticators, ball mills,roll mills, extruders and the like. Oxidative or thermal shearing ordegrading techniques are also useful and are known. Details of numerousprocedures for shearing polymers are given in U.S. Pat. No. 5,348,673which is hereby incorporated herein by reference for relevantdisclosures in this regard.

The graft copolymers are typically derived from hydrocarbon polymers.Because the graft copolymers are prepared by a free radical process, thegrafting process is adaptable to a wide variety of polymer substrates.The only limitation on the nature of the hydrocarbon polymer is that itcontain a hydrogen atom that is accessible and abstractable in thepresence of the free radical initiator. Appropriate hydrocarbon polymersinclude those which contain a measure of olefinic unsaturation, as wellas those which are substantially saturated. Included are hydrocarbonpolymers that contain terminal or penultimate carbon-carbon unsaturationresidues due to termination processes and those having backbone orpendant unsaturation due to the incorporation of diene monomers, as wellas polymers wherein such unsaturation has been intentionally reduced orremoved by chemical means, such as catalytic hydrogenation. Preferably,the hydrocarbon polymer will typically contain olefinic unsaturation,based on the total number of carbon to carbon bonds in the polymer, ofless than 5%. More preferably, the polymer will contain less than 2%,and usually no more than 1% residual unsaturation. Most preferably, thehydrocarbon polymer is substantially free of olefinic unsaturation.

Many hydrocarbon polymers, when manufactured, contain significantamounts of olefinic unsaturation. In order to reduce this unsaturation,they may be hydrogenated to reduce the amount of olefinic unsaturationto acceptable levels. Usually they are hydrogenated to such an extentthat the resulting hydrogenated polymer has olefinic unsaturation, basedon the total number of carbon to carbon bonds in the polymer, of lessthan 5%, preferably less than 2%, more preferably no more than 1%residual unsaturation. Most preferably, the hydrocarbon polymer isexhaustively hydrogenated. The polymer may contain aliphatic, aromaticor cycloaliphatic components, or mixtures thereof. Aromatic unsaturationis not considered olefinic unsaturation within the context of thisinvention. Depending on hydrogenation conditions, up to about 50% ofaromatic groups may be hydrogenated.

In preferred embodiments, the hydrocarbon polymer is an oil soluble ordispersible homopolymer or copolymer selected from the group consistingof:

(1) polymers and hydrogenated polymers of dienes;

(2) copolymers and hydrogenated copolymers of conjugated dienes withvinyl substituted aromatic compounds; moreover

(3) polymers of alpha-olefins having from 2 to about 28 carbon atoms;

(4) olefin-diene copolymers and hydrogenated analogs thereof; and

(5) star polymers.

These preferred polymers are described in greater detail hereinbelow.

(1) Polymers of Dienes

The hydrocarbon polymer may be a homopolymer or copolymer of one or moredienes or a hydrogenated homopolymer or copolymer of one or more dienes.The diene polymers in this application are preferably those which havebeen substantially hydrogenated, and contain little residualunsaturation.

The dienes may be conjugated such as isoprene, butadiene and piperylene,or non-conjugated, such as 1-4 hexadiene and dicyclopentadiene. Polymersof conjugated dienes are preferred. Such polymers are convenientlyprepared via free radical and anionic polymerization techniques.Emulsion techniques are commonly employed for free radicalpolymerization.

Hydrogenation is usually accomplished employing catalytic methods.Catalytic techniques employing hydrogen under high pressure and atelevated temperature are well-known to those skilled in the chemicalart.

An extensive discussion of hydrogenated diene polymers appears in the“Encyclopedia of Polymer Science and Engineering”, Volume 2, pp 550-586,and Volume 8, pp 499-532, Wiley-Interscience (1986), which is herebyexpressly incorporated herein by reference for relevant disclosures inthis regard.

Hydrogenated polymers include homopolymers and copolymers of conjugateddienes including polymers of 1,3-dienes of the formula

wherein each substituent denoted by R, or R with a numerical subscript,is independently hydrogen or hydrocarbon based, wherein hydrocarbonbased is as defined hereinabove. At least one substituent is H.Preferably, when R₃ is hydrocarbyl, R and R₁ will both be hydrogen, andwhen R₂ is hydrocarbyl, then R4 and R₅ will both be hydrogen. Mostpreferably, R₁, R₂, R₃ and R₄ will all be hydrogen. Normally, the totalcarbon content of the diene monomer will not exceed 20 carbons.Preferred dienes for preparation of the polymer are piperylene,isoprene, 2,3-dimethyl-1,3-butadiene, chloroprene and 1,3-butadiene.

Suitable homopolymers of conjugated dienes are described, and methodsfor their preparation are given in numerous U.S. patents, including thefollowing:

U.S. Pat. No. 3,547,821

U.S. Pat. No. 3,835,053

U.S. Pat. No. 3,959,161

U.S. Pat. No. 3,965,019

U.S. Pat. No. 4,085,055

U.S. Pat. No. 4,116,917

As a specific example, U.S. Pat. No. 3,959,161 teaches the preparationof hydrogenated polybutadiene. In another example, upon hydrogenation,1,4-polyisoprene becomes an alternating copolymer of ethylene andpropylene.

Copolymers of conjugated dienes are prepared from two or more conjugateddienes. Useful dienes are the same as those described in the preparationof homopolymers of conjugated dienes hereinabove. The following U.S.Patents describe diene copolymers and methods for preparing them:

U.S. Pat. No. 3,965,019

U.S. Pat. No. 4,073,737

U.S. Pat. No. 4,085,055

U.S. Pat. No. 4,116,917

For example, U.S. Pat. No. 4,073,737 describes the preparation andhydrogenation of butadiene-isoprene copolymers.

(2) Copolymers of Conjugated Dienes with Vinyl Substituted AromaticCompounds

In one embodiment, the hydrocarbon polymer is a copolymer of avinyl-substituted aromatic compound and a conjugated diene. In anotherembodiment, it is a hydrogenated copolymer of a vinyl-substitutedaromatic compound and a conjugated diene.

As used herein, the term copolymer refers to polymers derived from 2 ormore monomeric species. In this embodiment, one is a vinyl substitutedaromatic compound and the other is an aliphatic conjugated diene.

The vinyl substituted aromatics generally contain from 8 to about 20carbons, preferably from 8 to 12 carbon atoms and most preferably, 8 or9 carbon atoms.

Examples of vinyl substituted aromatics include vinyl anthracenes, vinylnaphthalenes and vinyl benzenes (styrenic compounds). Styrenic compoundsare preferred, examples being styrene, alpha-methystyrene, ortho-methylstyrene, meta-methyl styrene, para-methyl styrene,tertiary-butylstyrenes, chlorostyrenes, and chloromethyl styrenes, withstyrene being preferred.

The conjugated dienes generally have from 4 to about 10 carbon atoms andpreferably from 4 to 6 carbon atoms. Example of conjugated dienesinclude piperylene, 2,3-dimethyl-1,3-butadiene, chloroprene, isopreneand 1,3-butadiene, with isoprene and 1,3-butadiene being particularlypreferred. Mixtures of such conjugated dienes are useful.

The vinyl substituted aromatic content of these copolymers is typicallyin the range of about 20% to about 70% by weight, preferably about 40%to about 60% by weight. The aliphatic conjugated diene content of thesecopolymers is typically in the range of about 30% to about 80% byweight, preferably about 40% to about 60% by weight.

The polymers, and in particular, styrene-diene copolymers, can be randomcopolymers, regular block copolymers or random block copolymers. Randomcopolymers are those in which the comonomers are randomly, or nearlyrandomly, arranged in the polymer chain with no significant blocks(segments) of homopolymer of either monomer. Regular block copolymersare those in which a small number, usually one or two, of relativelylong chains of homopolymer of one type of monomer are alternately joinedto a small number, usually one or two, of relatively long chains ofhomopolymer of another type of monomer. Random block copolymers arethose in which a larger number of relatively short segments ofhomopolymer of one type of monomer alternate with relatively shortsegments of homopolymer of another monomer.

Other polymerization techniques such as emulsion polymerization can beused.

The random, regular block and random block polymers used in thisinvention may be linear, or they may be partially or highly branched.The relative arrangement of homopolymer segments in a linear regularblock or random block polymer is obvious. Differences in structure liein the number and relative sizes of the homopolymer segments; thearrangement in a linear block polymer of either type is alwaysalternating in homopolymer segments.

Normal or regular block copolymers usually have from 1 to about 5, often1 to about 3, preferably only from 1 to about 2 relatively largehomopolymer blocks of each monomer. Thus, a linear regular diblockcopolymer of styrene or other vinyl aromatic monomer (A) and diene (B)would have a general structure represented by a large block ofhomopolymer (A) attached to a large block of homopolymer (B), as:

(A)_(a)(B)_(b)

where a and b are as described hereinbelow. Techniques vary for thepreparation of these “A-B-A” and “B-A-B” triblock polymers, and aredescribed in the literature for anionic polymerization.

Similarly, a regular linear tri-block copolymer of styrene or othervinyl aromatic monomer (A) and diene monomer (B) may be represented, forexample, by

(A)_(a)(B)_(b)(A)_(c), or (B)_(a)(A)_(b)(B)_(c), or(A)_(a)(B)_(b)(C)_(c)

where (C) represents a segment of a third monomer. Severalconfigurations are possible depending on how the homopolymer segmentsare arranged with respect to each other. For example, linear triblockcopolymers of monomers (A), (B) and (C) can be represented by thegeneral configurations:

(A)_(a)-(B)_(b)-(C)_(c), (A)_(a)-(C)_(c)-(B)_(b), or(B_(b)-(A)_(a)-(C)_(c),

wherein the lower case letters a, b and c represent the approximatenumber of monomer units in the indicated block.

The sizes of the blocks are not necessarily the same, but may varyconsiderably. The only stipulation is that any regular block copolymercomprises relatively few, but relatively large, alternating homopolymersegments.

As an example, when (A) represents blocks derived from diene such asisoprene or butadiene, “a” usually ranges from about 100 to about 2000,preferably from about 500 to about 1500; when (B) represents, forexample, blocks derived from styrene, “b” usually ranges from about 100to about 2000, preferably from about 200 to about 1000; and when a thirdblock (C) is present, “c” usually ranges from about 10 to about 1000,provided that the {overscore (M)}_(n) of the polymer is within theranges indicated as useful for this invention.

The copolymers can be prepared by methods well known in the art. Suchcopolymers usually are prepared by anionic polymerization using Group Iametals in the presence of electron-acceptor aromatics, or preformedorganometallics such as sec-butyllithium as polymerization catalysts.

The styrene/diene block polymers are usually made by anionicpolymerization, using a variety of techniques, and altering reactionconditions to produce the most desirable features in the resultingpolymer. In an anionic polymerization, the initiator can be either anorganometallic material such as an alkyl lithium, or the anion formed byelectron transfer from a Group Ia metal to an aromatic material such asnaphthalene. A preferred organometallic material is an alkyl lithiumsuch as sec-butyl lithium; the polymerization is initiated by additionof the butyl anion to either the diene monomer or to the styrene.

When an alkyl lithium initiator is used, a homopolymer of one monomer,e.g., styrene, can be selectively prepared, with each polymer moleculehaving an anionic terminus, and lithium gegenion. The carbanionicterminus remains an active initiation site toward additional monomers.The resulting polymers, when monomer is completely depleted, willusually all be of similar molecular weight and composition, and thepolymer product will be “monodisperse” (i.e., the ratio of weightaverage molecular weight to number average molecular weight is verynearly 1.0). At this point, addition of 1,3-butadiene, isoprene or othersuitable anionically polymerizable monomer to thehomopolystyrene-lithium “living” polymer produces a second segment whichgrows from the terminal anion site to produce a living di-block polymerhaving an anionic terminus, with lithium gegenion.

Subsequent introduction of additional styrene can produce a new (polyA)-block-(poly B)-block-(poly A), or A-B-A triblock polymer; higherorders of block polymers can be made by consecutive stepwise additionsof different monomers in different sequences.

Alternatively, a living diblock polymer can be coupled by exposure to anagent such as a dialkyl dichlorosilane. When the carbanionic “heads” oftwo A-B diblock living polymers are coupled using such an agent,precipitation of LiCl occurs to give an A-B-A triblock polymer.

Block copolymers made by consecutive addition of styrene to give arelatively large homopolymer segment (A), followed by a diene to give arelatively large homopolymer segment (B), are referred to as (polyA)-block-(poly B) copolymers, or A-B diblock polymers.

When metal naphthalide is employed as initiator, the dianion formed byelectron transfer from metal, e.g., Na, atoms to the naphthalene ringcan generate dianions which may initiate polymerization, e.g. of monomerA, in two directions simultaneously.

Subsequent exposure of the poly (A) dianion to a second monomer (B)results in formation of a (poly B)-block-(poly A)-block-(poly B), or aB-A-B triblock polymeric dianion, which may continue to interact withadditional anionically-polymerizable monomers of the same, or differentchemical type, in the formation of higher order block polymers. Ordinaryblock copolymers are generally considered to have up to about 5 suchblocks.

Usually, one monomer or another in a mixture will polymerize faster,leading to a segment that is richer in that monomer, interrupted byoccasional incorporation of the other monomer. This can be used to builda type of polymer referred to as a “random block polymer”, or “taperedblock polymer. When a mixture of two different monomers is anionicallypolymerized in a non-polar paraffinic solvent, one will initiateselectively, and usually polymerize to produce a relatively shortsegment of homopolymer. Incorporation of the second monomer isinevitable, and this produces a short segment of different structure.Incorporation of the first monomer type then produces another shortsegment of that homopolymer, and the process continues, to give a“random” alternating distribution of relatively short segments ofhomopolymers, of different lengths. Random block polymers are generallyconsidered to be those comprising more than 5 such blocks. At somepoint, one monomer will become depleted, favoring incorporation of theother, leading to ever longer blocks of homopolymer, producing a“tapered block copolymer.” Intentional enrichment of a particularmonomer in the latter, high-conversion stages of polymerization is oftenused to assure a tapered block copolymer configuration.

An alternative way of preparing random or tapered block copolymersinvolves initiation of styrene, and interrupting with periodic, or step,additions of diene monomer. The additions are programmed according tothe relative reactivity ratios and rate constants of the styrene andparticular diene monomer.

“Promoters” are electron-rich molecules that facilitate anionicinitiation and polymerization rates while lessening the relativedifferences in rates between various monomers. Promoters also influencethe way in which diene monomers are incorporated into the block polymer,generally favoring 1,2-polymerization of dienes over the normal 1,4-cis-addition.

Hydrogenation of the unsaturated block polymers initially obtainedproduces polymers that are more oxidatively and thermally stable.Techniques for accomplishing hydrogenation are well known to those ofskill in the art. Briefly, hydrogenation is accomplished by contactingthe copolymers with hydrogen at superatmospheric pressures in thepresence of a metal catalyst such as colloidal nickel, palladiumsupported on charcoal, etc. and may be carried out as part of theoverall production process, using finely divided, or supported, nickelcatalyst. Other transition metals may also be used to effect thetransformation. Hydrogenation is normally carried out to reduceapproximately 94-96% of the olefinic unsaturation of the initialpolymer. In general, it is preferred that these copolymers, for reasonsof oxidative stability, contain no more than about 10%, preferably nomore than 5% and more preferably no more than about 0.5% residualolefinic unsaturation on the basis of the total amount of olefinicdouble bonds present in the polymer prior to hydrogenation. Suchunsaturation can be measured by a number of means well known to those ofskill in the art, such as infrared or nuclear magnetic resonancespectroscopy. Most preferably, these copolymers contain no significantolefinic unsaturation. Aromatic unsaturation is not considered to beolefinic unsaturation within the context of this invention.

Often the arrangement of the various homopolymer blocks is dictated bythe reaction conditions such as catalyst and polymerizationcharacteristics of the monomers employed. Conditions for modifyingarrangement of polymer blocks are well known to those of skill in thepolymer art. Literature references relating to polymerization techniquesand methods for preparing certain types of block polymers include:

1) “Encyclopedia of Polymer Science and Engineering”, Wiley-IntersciencePublishing, New York, (1986);

2) A. Noshay and J. E. McGrath, “Block Copolymers”, Academic Press, NewYork, (1977);

3) R. J. Ceresa, ed., “Block and Graft Copolymerization”, John Wiley andSons, New York, (1976); and

4) D. J. Meier, ed., (Block Copolymers”, MMI Press, Harwood AcademicPublishers, New York, (1979).

Each of these is hereby incorporated herein by reference for relevantdisclosures relating to block copolymers.

Examples of suitable regular diblock copolymers as set forth aboveinclude SHELLVIS® 40, and SHELLVIS® 50, both hydrogenatedstyrene-isoprene linear diblock copolymers, manufactured by ShellChemical.

Examples of commercially available random block and tapered random blockcopolymers include the various GLISSOVISCAL® block copolymersmanufactured by BASF. A previously available random block copolymer wasPhil-Ad viscosity improver, manufactured by Phillips Petroleum.

The copolymers preferably have number average molecular weights({overscore (M)}_(n)) in the range of about 20,000 to about 500,000,more preferably from about 30,000 to about 150,000. The weight averagemolecular weight ({overscore (M)}_(w)) for these copolymers is generallyin the range of about 25,000 to about 500,000, preferably from about50,000 to about 300,000, with characteristic narrow polydispersities(ratio of {overscore (M)}_(w) to {overscore (M)}_(n)) of about 1.0 toabout 1.4.

(3) Polymers of Alpha-Olefins

Another hydrocarbon polymer which can be grafted is a polyolefin, whichconsists in its main chain essentially of alpha olefin monomers. Thepolyolefins of this embodiment thus exclude polymers which have a largecomponent of other types of monomers copolymerized in the main polymerbackbone, such as ester monomers, acid monomers, and the like. Thepolyolefin may contain impurity amounts of such materials, e.g., lessthan 5% by weight, more often less than 1% by weight, preferably, lessthan 0.1% by weight of other monomers. Useful polymers include oilsoluble or dispersible substantially saturated, including hydrogenated,polymers of alpha-olefins. By substantially saturated is meant that nomore than about 5% of the carbon to carbon bonds in the polymer areunsaturated. Preferably, no more than 1% are unsaturated, morepreferably, the polymer is essentially free of unsaturation.

These polymers are preferably copolymers, more preferably copolymers ofethylene and at least one other α-olefin having the formula CH₂═CHR₁wherein R₁ is straight chain or branched chain alkyl radical comprising1 to 26 carbon atoms. Preferably R₁ in the above formula is alkyl offrom 1 to 8 carbon atoms, and more preferably is alkyl of from 1 to 2carbon atoms.

The ethylene content is preferably in the range of 20 to 80 percent byweight, and more preferably 30 to 70 percent by weight. When propyleneand/or 1-butene are employed as comonomer(s) with ethylene, the ethylenecontent of such copolymers is most preferably 45 to 65 percent, althoughhigher or lower ethylene contents may be present. Most preferably, thesepolymers are substantially free of ethylene homopolymer, although theymay exhibit a degree of crystallinity due to the presence of smallcrystalline polyethylene segments within their microstructure. Preferredpolymers are copolymers of ethylene and propylene and ethylene and1-butene.

The alpha olefin copolymer preferably has a number average molecularweight ({overscore (M)}_(n)) determined by gel-permeation chromatographyemploying polystyrene standards, ranging from about 30,000 to about300,000, more often from about 50,000 to about 150,000, even more oftenfrom about 80,000 to 150,000. Exemplary polydispersity values({overscore (M)}_(w)/{overscore (M)}_(n)) range from about 2.2 to about2.5.

The polymers employed in this embodiment may generally be preparedsubstantially in accordance with procedures which are well known in theart. The polymers for use in this embodiment can be prepared bypolymerizing monomer mixtures comprising alpha-olefins. The monomers arealpha-olefins containing from 2 to about 28 carbon atoms, and may bebranched chain or linear. In a preferred embodiment, one monomer isethylene, the comonomer being at least one C₃₋₂₈ alpha olefin,preferably C₃₋₈ alpha olefins. including monoolefins such as propylene,1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene,1-decene, propylene tetramer, diisobutylene, and triisobutylene.

Catalysts employed in the production of the reactant polymers arelikewise well known. One broad class of catalysts particularly suitablefor polymerization of α-olefins, comprises coordination catalysts suchas Ziegler or Ziegler-Natta catalysts comprising a transition metalatom. Ziegler-Natta catalysts are composed of a combination of atransition metal atom with an organo aluminum halide and may be usedwith additional complexing agents.

Polymerization using coordination catalysis is generally conducted attemperatures ranging between 20° and 300° C., preferably between 30° and200° C., often up to about 100° C. Reaction time is not critical and mayvary from several hours or more to several minutes or less, dependingupon factors such as reaction temperature, the monomers to becopolymerized, and the like. One of ordinary skill in the art mayreadily obtain the optimum reaction time for a given set of reactionparameters by routine experimentation. Preferably, the polymerizationwill generally be completed at a pressure of 1 to 40 MPa (10 to 400bar).

The polymerization may be conducted employing liquid monomer, such asliquid propylene, or mixtures of liquid monomers (such as mixtures ofliquid propylene and 1-butene), as the reaction medium. Alternatively,polymerization may be accomplished in the presence of a hydrocarboninert to the polymerization such as butane, pentane, isopentane, hexane,isooctane, decane, toluene, xylene, and the like.

When carrying out the polymerization in a batch-type fashion, thereaction diluent (if any) and the alpha-olefin comonomer(s) are chargedat appropriate ratios to a suitable reactor. Care should be taken thatall ingredients are dry, with the reactants typically being passedthrough molecular sieves or other drying means prior to theirintroduction into the reactor. Subsequently, component(s) of thecatalyst are introduced while agitating the reaction mixture, therebycausing polymerization to commence. Alternatively, component(s) of thecatalyst may be premixed in a solvent and then fed to the reactor. Aspolymer is being formed, additional monomers may be added to thereactor. Upon completion of the reaction, unreacted monomer and solventare either flashed or distilled off, if necessary by vacuum, and thecopolymer withdrawn from the reactor.

The polymerization may be conducted in a continuous manner bysimultaneously feeding the reaction diluent (if employed), monomers,component(s) of the catalyst to a reactor and withdrawing solvent,unreacted monomer and polymer from the reactor so as to allow aresidence time of ingredients long enough for forming polymer of thedesired molecular weight; and separating the polymer from the reactionmixture.

In those situations wherein the molecular weight of the polymer productthat would be produced at a given set of operating conditions is higherthan desired, any of the techniques known in the prior art for controlof molecular weight, such as the use of hydrogen and/or polymerizationtemperature control, may be used.

However, the polymers are preferably formed in the substantial absenceof added H₂ gas, that is H₂ gas added in amounts effective tosubstantially reduce the polymer molecular weight.

The polymers can be random copolymers, block copolymers, and randomblock copolymers. Ethylene propylene copolymers are usually randomcopolymers.

Numerous United States patents, including the following, describe thepreparation of copolymers of alpha olefins.

3,513,096 4,068,057 3,551,336 4,081,391 3,562,160 4,089,794 3,607,7494,098,710 3,634,249 4,113,636 3,637,503 4,132,661 3,992,310 4,137,1854,031,020 4,138,370 4,068,056 4,144,181

Copolymers of ethylene with higher alpha olefins are the most cornmoncopolymers of aliphatic olefins and ethylene-propylene copolymers arethe most common ethylene-alpha-olefin copolymers and are preferred foruse in this invention. A description of an ethylene-propylene copolymerappears in U.S. Pat. No. 4,137,185 which is hereby incorporated hereinby reference.

Useful ethylene-alpha olefin, usually ethylene-propylene, copolymers arecommercially available from numerous sources including the Exxon, Texacoand Lubrizol Corporations.

(4) Olefin-Diene Copolymers

Another useful hydrocarbon monomer is one derived from olefins,especially lower olefins, and dienes. Dienes may be non-conjugated orconjugated. Useful olefins and dienes are the same as those describedhereinabove and hereinafter in discussions of other polymer types.

In one embodiment, the copolymer is an ethylene-lower olefin-dienecopolymer. As used herein, the term lower refers to groups or compoundscontaining no more than 8 carbon atoms. Preferably, the diene isnon-conjugated.

There are numerous commercial sources for lower olefin-diene polymers.For example, ORTHOLEUM® 2052 (a product marketed by the DuPont Company)which is a terpolymer having an ethylene:propylene weight ratio of about57:43 and containing 4-5 weight % of groups derived from 1-4 hexadienemonomer, and numerous other such materials are readily available.Olefin-diene copolymers and methods for their preparation are describedin numerous patents including the following U.S. Patents:

U.S. Pat. No. 3,291,780

U.S. Pat. No. 3,300,459

U.S. Pat. No. 3,598,738

U.S. Pat. No. 4,026,809

U.S. Pat. No. 4,032,700

U.S. Pat. No. 4,156,061

U.S. Pat. No. 3,320,019

U.S. Pat. No. 4,357,250

U.S. Pat. No. 3,598,738, which describes the preparation ofethylene-propylene-1,4-hexadiene terpolymers, is illustrative. Thispatent also lists numerous references describing the use of variouspolymerization catalysts.

Another useful polymer is an olefin-conjugated diene copolymer. Anexample of such a polymer is butyl rubber, an isobutylene-isoprenecopolymer. Butyl rubbers are produced using acidic catalysts, such asaluminum chloride, boron trifluoride, and other Lewis acids.

Details of various types of polymers, reaction conditions, physicalproperties, and the like are provided in the above patents and innumerous books, including:

“Riegel's Handbook of Industrial Chemistry”, 7th edition, James A. KentEd., Van Nostrand Reinhold Co., New York (1974), Chapters 9 and 10,

P. J. Flory, “Principles of Polymer Chemistry”, Cornell UniversityPress, Ithaca, N.Y. (1953),

“Kirk-Othmer Encyclopedia of Chemical Technology”, 3rd edition, Vol. 8(Elastomers, Synthetic, and various subheadings thereunder), John Wileyand Sons, New York (1979).

Each of the above-mentioned books and patents is hereby expresslyincorporated herein by reference for relevant disclosures containedtherein.

Polymerization can also be effected using free radical initiators in awell-known process, generally employing higher pressures than used withcoordination catalysts.

(5) Star Polymer

Star polymers are polymers comprising a nucleus and polymeric arms.Common nuclei include polyalkenyl compounds, usually compounds having atleast two non-conjugated alkenyl groups, usually groups attached toelectron withdrawing groups, e.g., aromatic nuclei. The polymeric armsare often homopolymers and copolymers of conjugated dienes andmonoalkenyl arenes and mixtures thereof.

The polymers thus comprise a poly(polyvinylic) coupling agent nucleuswith polymeric arms extending outward therefrom. The star polymers areusually hydrogenated such that at least 80% of the covalentcarbon-carbon bonds are saturated, more often at least 90% and even morepreferably, at least 95% are saturated.

The polyvinylic compounds making up the nucleus are illustrated bypolyalkenyl arenes, e.g., divinyl benzene and poly vinyl aliphaticcompounds.

Dienes making up the polymeric arms are illustrated by, butadiene,isoprene and the like. Monoalkenyl compounds include, for example,styrene and alkylated derivatives thereof.

Star polymers are well known in the art. Such material and methods forpreparing same are described in numerous publications and patents,including the following United States patents which are herebyincorporated herein by reference for relevant disclosures containedtherein:

U.S. Pat. No. 4,116,917,

U.S. Pat. No. 4,141,847,

U.S. Pat. No. 4,346,193,

U.S. Pat. No. 4,358,565,

and U.S. Pat. No. 4,409,120.

Star polymers are commercially available, for example as SHELLVIS® 200sold by Shell Chemical Co.

The aforementioned hydrocarbon polymers can also be prepared employing aclass of catalysts referred to as metallocene catalysts, or constrainedgeometry catalysts. Polymers prepared using these catalysts tend to havelower polydispersity values arising from more narrow molecular weightdistributions than, for example, those derived from more conventionalZiegler-Natta catalyst derived polymers.

Nitrogen Containing Monomers

The hydrocarbon polymer backbone, while contributing to theviscosity-improving characteristics of the products of this invention,by itself contributes little toward dispersancy in lubricants. Thenitrogen containing units which are derived from nitrogen containingmonomers provide the bulk of the contribution toward dispersancyproperties of the dispersant viscosity improvers of this invention.

The (Meth)Acrylamide Monomer

One of the nitrogen containing units graft polymerized onto thehydrocarbon backbone is derived from at least one of a neutral N-(lowerhydrocarbyl group)- or a neutral N,N-di-(lower hydrocarbyl group)-(meth)acrylamide. By “neutral” is meant that the (meth)acrylamide doesnot contain any additional amine site which contributes to basicity inthe sense of a titratable amino group.

The expression “(meth)acrylamide” with “meth” included withinparenthesis, includes both acrylamides and methacrylarnides. Theexpression “acrylamide” used alone does not include methacrylamides.Likewise, the expression “methacrylamide” where “meth” is not includedwithin parenthesis does not include acrylamides.

Each lower hydrocarbyl group substituent on the nitrogen of the amidegroup contains no more than 7 carbon atoms, and the total number ofcarbon atoms in the lower hydrocarbyl groups does not exceed 9. Thus,for example, an N-alkyl substituted(meth)acrylamide may contain amaximum of seven carbon atoms in the alkyl group. The total number ofcarbon atoms in the two alkyl groups of an N,N-dialkyl (meth)acrylamidedoes not exceed 9.

The N-hydrocarbyl group substituents may be aromatic and aliphatic,including cycloaliphatic, groups, preferably aliphatic groups and mostpreferably, alkyl groups.

Each lower hydrocarbyl group may contain up to one oxygen or sulfurcontaining group or atom. Such groups include ether groups, thioethergroups, carboxylic acid groups, ester groups, keto carbonyl groups,aldehyde groups, mercapto groups and alcohol groups. The total number ofcarbon atoms in these groups includes carbon atoms making up the heterogroups such as carbonyl carbons, etc.

Illustrative (meth)acrylamide monomers include N-phenyl acrylamide,N-phenyl-N-methyl acrylamide, N-methyl acrylamide,N,N-dimethylacrylamide, N-allyl acrylamide, N-(t-butyl) acrylamide,N-heptyl acrylamide, N-methyl-N-heptyl acrylamide, N-propyl acrylamide,N,N-diethyl acrylamide, diacetone acrylamide, and the correspondingmethacrylamides such as N-methyl- and N,N-dimethyl methacrylamide, andthe like. Preferred are N-methyl-, N-ethyl-, N,N-dimethyl-,N,N-diethyl-, and N-t-butyl-(meth)acrylamides and diacetone acrylamide.

The Vinylic Nitrogen Containing Heterocycle

The other nitrogen containing units graft polymerized onto thehydrocarbon backbone are derived from at least one free radicalpolymerizable vinylic nitrogen containing heterocyclic monomer. Theseinclude both N-vinyl and C-vinyl nitrogen containing heterocyclics.

Examples of these include N-vinyl carbazole, the vinylpyridines, N-vinylpyrrolidinone, N-vinyl thiopyrrodinone, N-vinyl oxazolidinone, N-vinylimidazole, the 2-vinyl dihydro-oxazines, 2-vinyl oxazoles, 2-vinyloxazolines, N-vinyl caprolactam, vinyl piperazine, and the like. N-vinylimidazole and N-vinyl pyrrolidone are preferred.

N-vinyl imidazole is particularly difficult to graft polymerize ontonon-polar hydrocarbon polymers. The process of co-grafting with theacrylamide monomers, particularly N-methyl acrylamide, N-ethylacrylamide and N,N-dimethylacrylamide, is especially useful.

The graft copolymers of this invention have from about 0.25 to about 5moles, preferably from about 0.5 to about 4 moles, and especially fromabout 1 to about 3 moles of (meth)acrylamide units per mole of vinylicnitrogen containing heterocyclic units.

The graft copolymer comprises a total of from about 0.2 to about 5moles, preferably from about 0.4 to about 3 moles, and more often fromabout 0.5 to about 2 moles nitrogen containing units per 10,000 weightaverage ({overscore (M)}_(w)) molecular weight units of hydrocarbonpolymer.

The Process

The graft copolymers of this invention can be prepared by a processwhich comprises simultaneously grafting onto a hydrocarbon polymer,under free radical conditions, at least two nitrogen containingmonomers, wherein one of the monomers comprises at least one of aneutral N-(lower hydrocarbyl group)- (meth)acrylamide and a neutralN,N-di-(lower hydrocarbyl group)- (meth)acrylamide and one of themonomers comprises at least one vinylic nitrogen containing heterocycliccompound. Exemplary and preferred hydrocarbon polymers and nitrogencontaining monomers are those set forth hereinabove.

The grafting is conducted under free radical conditions employing a freeradical initiator. Free radical initiators are described in detalhereinbelow.

The grafting process is typically conducted at an elevated temperature,generally from about 85° C. up to the lowest decomposition temperatureof reactants or product, preferably from about 100° C. to about 165° C.and more preferably from about 120° C. to about 145° C. Considerationsfor determining reaction temperatures include reactivity of the systemand the half-life of the initiator at a particular temperature.

Free Radical Initiators

As noted herein, the graft polymerizations providing the graftcopolymers of this invention are conducted under free radical conditionsemploying a free radical initiator. A wide variety of free radicalinitiators, sometimes referred to as free radical generating reagents,are well known to those skilled in the art. These include diazocompounds, peroxy compounds, nitroxyl radicals and high energyradiation. Radical grafting is preferably carried out using free radicalinitiators such as peroxides, hydroperoxides, diacyl peroxides, peroxyesters and azo compounds which decompose thermally within the graftingtemperature range to provide said free radicals.

Numerous free-radical initiators are mentioned in the above-referencedtests by Flory and by Bovey and Winslow. An extensive listing offree-radical initiators appears in J. Brandrup and E. H. Immergut,Editor, “Polymer Handbook”, 2nd edition, John Wiley and Sons, New York(1975), pages II-1 to II-40. Preferred free radical generating reagentsinclude t-butyl peroxide, t-butylhydroperoxide, t-butyl perbenzoate,t-amyl peroxide, cumyl peroxide, t-butyl peroctoate,t-butyl-m-chloroperbenzoate, benzoyl peroxide,sec-butylperoxydicarbonate, azobisisobutyronitrile, andazobisisovaleronitrile.

The free-radical initiators are generally used in an amount from about0.01 to about 10 percent by weight based on the total weight of thereactants. Preferably, the initiators are used at about 0.05 to about 1percent by weight.

The choice of free radical generating reagent can be an importantconsideration. For example, when a polymer undergoing grafting with amonomer is diluted with a solvent such as a hydrocarbon oil, grafting ofthe monomer onto the oil diluent may occur. It has been observed thatthe choice of initiator affects the extent of grafting of the monomeronto the oil diluent. Reducing the amount of monomer grafted onto thediluent usually results in an increased amount of monomer grafted ontothe polymer. Improved efficiency of monomer grafting onto substantiallysaturated copolymer resins has been described by Lange et al., in U.S.Pat. No. 5,298,565 which is hereby incorporated herein by reference forrelevant disclosures in this regard.

Azo group containing initiators, such as Vazo® polymerization initiators(DuPont) employed in the grafting process at about 95° C. result in amuch higher degree of grafting onto the polymer than do peroxideinitiators such as t-butyl peroxide, employed at about 150-160° C.Peresters are particularly effective in the free-radical graftingprocess.

The grafting may be conducted in solution. The solvent may comprise awide variety of materials but preferred are hydrocarbon solvents.Preferably, the grafting is conducted employing a generally non-reactivesolvent or diluent; i.e., one which does not undergo any significantreaction with any of the reactants or products of this invention.Particularly useful solvents/diluents include substantially saturatedaliphatic solvents that are relatively free of abstractable tertiary,allylic or benzylic hydrogen atoms. Specific examples includehydrorefined and hydrotreated mineral oils, polyalphaolefins, volatilealkanes, and the like. Use of these solvents prevents significantgrafting of the nitrogen-containing monomers onto the diluent. While formany applications the choice of solvent is not critical, it isparticularly preferred that when the graft copolymer is intended for useas a dispersant viscosity improver for lubricating oil compositions, thea solvent, if used, is a non-reactive solvent.

Diluents that are not highly saturated, for example, napthenic oils, maybe used. However, when these diluents are used, the products obtainedfrequently suffer from reduced grafting onto the hydrocarbon polymer.This can be alleviated to some extent by employing additional monomerreactant to increase the number of monomers grafted onto the polymer.

A variety of solvents may be used including those which are sufficientlyvolatile such that they may be conveniently removed from the graftcopolymer. Alternatively, the reaction may be conducted in an oil oflubricating viscosity which then serves as a diluent to facilitatehandling of materials during preparation of the copolymer and of theresulting copolymer. Copolymers containing a lubricating oil as diluentmay also be prepared by simultaneously removing a volatile diluent andreplacing same with an oil of lubricating viscosity.

In an alternative embodiment, the copolymer may be prepared byconducting the reaction in an extruder which provides mechanical shear.When an extruder is employed, a neat (diluent free) product may beobtained.

The following examples are intended to illustrate several compositionsof this invention as well as means for preparing same. Unless indicatedotherwise, all parts are parts by weight, temperatures are in degreesCelsius (° C.), and pressures are atmospheric. When referring to partsby volume, the relationship is as parts by weight in grams to parts byvolume in milliliters. Filtrations are conducted using a diatomaceousearth filter aid. All analytical values are by analysis. Viscosity ismeasured using ASTM-D445 procedure. It is to be understood that theseexamples are only intended to illustrate compositions and procedures ofthe invention and are not intended to limit the scope of the invention.

EXAMPLE 1

A reactor equipped with a stirrer, thermometer, water cooled refluxcondenser and sub-surface gas inlet is charged with 3000 parts of a 10%by weight in mineral oil (PetroCanada 100N, ˜100% saturated) solution ofan ethylene-propylene-dicyclopentadiene copolymer having {overscore(M)}_(n) 89,000 and {overscore (M)}_(w) 200,000 comprising 51 weight %ethylene units and 2 weight % dicyclopentadiene units. The materials areheated, under N₂ to 130° C. To one addition funnel are added a mixtureof 7.5 parts N-vinyl imidazole and 15 parts N,N-dimethyl acrylamide in50 parts by volume toluene and to a second addition funnel are added 15parts t-butyl peroxybenzoate in 25 parts by volume toluene. Whilemaintaining N₂, the two toluene solutions are added dropwise,simultaneously, over 2 hours. After the additions are completed, thematerials are heated while maintaining N₂, at 130° C. for 4 hours,stripped to 150° C. then vacuum stripped to 150° C. at 20 mm Hgpressure. The residue is filtered providing a product containing 0.158%N, total base number=1.28 and kinematic viscosity (100° C.) 2830centistokes.

EXAMPLE 2

A mixture of 610 parts of the product of Example 1 and 6.1 parts of an85% active primary straight chain alkyl benzene sulfonic acid arestirred, under N₂, at 130° C. for 2 hours. Kinematic viscosity (100°C.)=4200 centistokes.

EXAMPLE 3

A reactor equipped with a stirrer, thermometer, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 9% byweight in mineral oil (Exxon 100N, ˜75% saturated) solution of anethylene-propylene-dicyclopentadiene copolymer having {overscore(M)}_(n) 140,000 and {overscore (M)}_(w) 330,000 comprising 51 weight %ethylene units and 2 weight % dicyclopentadiene units. The materials areheated, under N₂, to 130° C. To a first addition funnel are charged 1.5parts 1-vinylimidazole, 3 parts N,N-dimethylacrylamide and 14 partstoluene. To a second addition funnel are charged 4.5 parts t-butylperoxybenzoate and 14 parts toluene. While maintaining N₂ throughout thereaction, dropwise addition of the peroxybenzoate is begun followed 0.1hour later by dropwise addition of the monomers. Dropwise addition fromthe two addition funnels is carried out for 1.25 hours then the batch isheld at 135° C. for 2.5 hours. The apparatus is then set up forstripping. The materials are purged with N₂ and heated to 145° C. whilecollecting 10.3 parts distillate. The product contains 0.07% N.

EXAMPLE 4

The procedure of Example 3 is repeated with 1000 parts of the polymersolution, 2.25 parts 1-vinylimidazole, 4.5 parts N,N-dimethylacrylamideand 4.8 parts t-butyl peroxybenzoate. Toluene is used in sufficientamount to bring the volume in each addition funnel to 20 parts byvolume. Product contains 0.125% N.

EXAMPLE 5

The procedure of Example 3 is repeated with 1000 parts of the polymersolution, 1.5 parts 1-vinylimidazole, 3 parts N,N-dimethylacrylamide and4.5 parts t-butyl peroxybenzoate. The additions are completed in 0.7hour. After the initial 2.5 hour heating period, an additional 0.5 partt-butyl peroxybenzoate is added and heating at 135° C. is continued for3 more hours. The product contains 0.09% N.

EXAMPLE 6

The procedure of Example 3 is repeated except the polymer is dissolvedin PetroCanada 100N mineral oil (˜100% saturated). The product contains0.04% N.

EXAMPLE 7

A reactor equipped with a stirrer, thermowell, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 10% byweight in mineral oil (150N, ˜88% saturated) solution of a hydrogenatedstyrene-butadiene random block copolymer having molecular weightdetermined by GPC of about 120,000 (GLISSOVISCAL® 5260, BASF). Thematerials are heated, under N₂, to 130° C. To a first addition funnelare charged 1.67 parts 1-vinylimidazole, 3.33 partsN,N-dimethylacrylamide and 15 parts toluene. To a second addition funnelare charged 5.5 parts t-butyl peroxybenzoate and 15 parts toluene. Whilemaintaining N₂ throughout the reaction, dropwise addition of theperoxybenzoate is begun followed 0.1 hour later by dropwise addition ofthe monomers. Dropwise addition from the two addition funnels is carriedout simultaneously and is completed in 1.3 hours. After addition iscompleted, the batch is heated to 135° C. and is held for 2 hours. Anadditional 1 part t-butyl peroxybenzoate is added and the batch ismaintained at 135° C. for 2 hours, N₂ blown at 145C for 3 hourscollecting 10 parts distillate, then filtered. The material contains0.09% N.

EXAMPLE 8

A reactor equipped with a stirrer, thermowell, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 10% byweight in mineral oil (PetroCanada 100N, ˜100% saturated) solution ofthe hydrogenated copolymer of Example 7. The materials are heated, underN2, to 130° C. To a first addition funnel are charged 1.67 parts1-vinylimidazole, 3.33 parts N,N-dimethylacrylamide and 15 partstoluene. To a second addition funnel are charged 5.5 parts t-butylperoxybenzoate and 15 parts toluene. While maintaining N₂ throughout thereaction, dropwise addition of the peroxybenzoate is begun followed 0.1hour later by dropwise addition of the monomers. Dropwise addition fromthe two addition funnels is carried out simultaneously and is completedin 1.25 hours. After addition is completed, the batch is heated to 135°C. and is held for 3.5 hours, then is heated to 145° C. and N₂ blown for2 hours, collecting 11 parts distillate. The product contains 0.09% N.

EXAMPLE 9

A reactor equipped with a stirrer, thermowell, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 9% byweight in mineral oil (100N, ˜78% saturated) solution of a hydrogenatedstyrene-butadiene linear tapered block copolymer having molecular weightdetermined by GPC of about 140,000 (GLISSOVISCAL® SGH, BASF). Thematerials are heated, under N₂, to 130° C. To a first addition funnelare charged 1.5 parts 1-vinylimidazole, 3.0 parts N,N-dimethylacrylamideand 15 parts toluene. To a second addition funnel are charged 5.0 partst-butyl peroxybenzoate and 15 parts toluene. While maintaining N₂throughout the reaction, dropwise addition of the peroxybenzoate isbegun followed 0.1 hour later by dropwise addition of the monomers.Dropwise addition from the two addition funnels is carried outsimultaneously and is completed in 1.25 hours. After addition iscompleted, the batch is heated to 135° C. and is held for 2.5 hoursfollowed by N₂ blowing at 145° C. for 3 hours while collecting 5 partsdistillate. The batch contains 0.077% N.

EXAMPLE 10

A reactor equipped with a stirrer, thermowell, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 7% byweight in mineral oil (100N, ˜79% saturated) solution of a hydrogenatedstyrene-isoprene linear diblock copolymer having molecular weightdetermined by GPC of about 200,000 (SHELLVIS® 40 Shell Chemical Co.).The materials are heated, under N₂, to 130° C. To a first additionfunnel are charged 1.17 parts 1-vinylirnidazole, 2.33 partsN,N-dimethylacrylamide and 15 parts toluene. To a second addition funnelare charged 4.5 parts t-butyl peroxybenzoate and 15 parts toluene. Whilemaintaining N2 throughout the reaction, dropwise addition of theperoxybenzoate is begun followed 0.1 hour later by dropwise addition ofthe monomers. Dropwise addition from the two addition funnels is carriedout simultaneously and is completed in 1.25 hours. After addition iscompleted, the batch is heated at 135° C. for 2.5 hours then is N₂ blownat 145° C. for 3 hours. The product contains 0.062% N.

EXAMPLE 11

A reactor equipped with a stirrer, thermowell, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 14% byweight in mineral oil (100N, ˜79% saturated) solution of a hydrogenatedisoprene radial copolymer having molecular weight determined by GPCusing polystyrene standard of about {overscore (M)}_(n)=414,000 and{overscore (M)}_(w)=541,000, (SHELLVIS® 250, Shell Chemical. Co.). Thematerials are heated, under N₂, to 130° C. To a first addition funnelare charged 2.33 parts 1-vinylimidazole, 4.67 partsN,N-dimethylacrylamide and 15 parts toluene. To a second addition funnelare charged 7 parts t-butyl peroxybenzoate and 15 parts toluene. Whilemaintaining N₂ throughout the reaction, dropwise addition of theperoxybenzoate is begun followed 0.1 hour later by dropwise addition ofthe monomers. Dropwise addition from the two addition funnels isconducted simultaneously for 1.25 hours then the batch is heated at 135°C. for 2.5 hours then N₂ blown at 145° C. for 2 hours while collecting 5parts distillate. The residue is filtered. The product contains 0.12% N.

EXAMPLE 12

The procedure of Example 11 is repeated employing 900 parts of a 14% byweight in mineral oil (PetroCanada 100N, ˜100% saturated) solution ofShellvis 250 polymer, 2.10 parts 1-vinylimidazole, 4.20 partsN,N-dimethylacrylamide, 6.3 parts t-butyl peroxybenzoate and, in eachaddition funnel, 15 parts toluene. After addition of monomers andinitiator, the material are heated at 130° C. for 4 hours then N₂ purgedat 145° C. for 2 hours while collecting 12 parts distillate. The productcontains 0.14% N.

Comparative Example

A reactor equipped with a stirrer, thermometer, water cooled refluxcondenser and sub-surface gas inlet is charged with 1000 parts of 14.5%by weight in mineral oil (Exxon 100N, ˜75% saturated) solution of anethylene-propylene-dicyclopentadiene copolymer having {overscore(M)}_(n) 140,000 and {overscore (M)}_(w) 330,000 comprising 51 weight %ethylene units and 2 weight % dicyclopentadiene units and 350 parts ofthe Exxon 100N mineral oil. The solution is heated, under N₂, to 80° C.whereupon 150 parts toluene and 2.5 parts n-dodecyl mercaptan. To afirst addition funnel is charged 10 parts N-vinylimidazole dissolved in25 parts toluene. To a second addition funnel is charged 7.5 partst-butyl peroxybenzoate dissolved in 25 parts toluene. The temperature isincreased to 130° C. then while maintaining N₂ throughout the reaction,simultaneous dropwise addition of the peroxybenzoate and theN-vinylimidazole from the two addition funnels is carried out for 1.5hours then the batch is held at 130° C. for 2.5 hours while maintainingN₂. The apparatus is then set up for stripping. The materials are vacuumstripped to 145° C. and 20 mm Hg, diluted with an additional Exxon 100Noil and filtered distill. The product contains 0.043% N.

The products of these Examples are evaluated using a screening testdesigned to determine the relative dispersancy of dispersants anddispersant viscosity improvers. Each is dissolved in a 100N mineral oilat several different active (neat, diluent free) chemical levels. Afixed amount of sludge solution is incorporated into the samples. Afterstanding for a period of time, each is examined to determine which isthe first in each series to exhibit fallout of the sludge. The firstsample number to experience fallout is report. Results are reported asnumbers ranging from ≦1 to ≧6 where ≦1 signifies a result where falloutis observed at the highest level of dispersant and ≧6 signifies a resultwhere fallout is not observed even at the lowest dispersant level.Results of the tests are reported in the following table:

Product of Example Rating 1 >6  2 6 3 5 4 5 5 4 6 >6  7 4 8 5 9 4 10 <1  11  5 12  6

Lubricating oil compositions of this invention comprise a major amountof an oil of lubrication viscosity and a minor amount of the nitrogencontaining graft copolymers of this invention. A major amount is thegreatest amount. For example, a composition containing 40% by weight ofan oil of lubricating viscosity, and the balance being made up of avariety of other materials, each present in amount less that 40% byweight of the composition, is considered as comprising a major amount ofan oil of lubricating viscosity. More frequently, a major amount ismeant more than 50% of the total weight of a composition. Thus, forexample, 51%, 80% and 99% are major amounts, and minor amounts are lessthan 50% by weight. Corresponding example of minor amounts are 1%, 20%and 49%. Generally, the lubricating oil compositions of this inventioncomprise a minor, viscosity improving and dispersant amount of the graftcopolymer. Typically, lubricating oil compositions of this inventioncomprise, on a neat chemical basis, from about 0.01 to about 10% byweight, more often from about 0.20% to about 5% by weight of thenitrogen containing copolymer.

This invention also relates to a method for improving the viscometricsand dispersancy characteristics of a lubricating oil composition, saidmethod comprising incorporating therein a minor, viscosity improving anddispersant amount of the graft copolymers of this invention.

Other Additives

Additive concentrates and lubricating oil compositions of this inventionmay contain other additives. The use of such additives is optional andthe presence thereof in the compositions of this invention will dependon the particular use and level of performance required. Thus the otheradditive may be included or excluded. Additive concentrates typicallycomprise from about 5% to about 80% by weight of interpolymer and fromabout 20% to about 95% by weight of a substantially, inert, normallyliquid, organic diluent.

Lubricating oil compositions often comprise zinc salts of adithiophosphoric acid, often referred to as zinc dithiophosphates, zincO,O-dihydrocarbyl dithiophosphates, and other commonly used names. Theyare sometimes referred to by the abbreviation ZDP. One or more zincsalts of dithiophosphoric acids may be present in a minor amount toprovide additional extreme pressure, anti-wear and anti-oxidancyperformance.

Other additives that may optionally be used in the lubricating oils ofthis invention include, for example, detergents, dispersants,supplemental viscosity improvers, oxidation inhibiting agents, corrosioninhibiting agents, pour point depressing agents, extreme pressureagents, anti-wear agents, color stabilizers, friction modifiers, andanti-foam agents. Extreme pressure agents and corrosion and oxidationinhibiting agents which may be included in the compositions of theinvention are exemplified by chlorinated aliphatic hydrocarbons, organicsulfides and polysulfides, phosphorus esters including dihydrocarbon andtrihydrocarbon phosphites, molybdenum compounds, and the like.

Other oxidation inhibiting agents include materials such as alkylateddiphenyl amines, hindered phenols, especially those having tertiaryalkyl groups such as tertiary butyl groups in the position ortho to thephenolic -OH group, and others. Such materials are well known to thoseof skill in the art.

Auxiliary viscosity improvers (also sometimes referred to as viscosityindex improvers or viscosity modifiers) may be included in thecompositions of this invention. Viscosity improvers are usuallypolymers, including polyisobutenes, polymethacrylic acid esters,hydrogenated diene polymers, polyalkyl styrenes, esterifiedstyrene-maleic anhydride copolymers, hydrogenatedalkenylarene-conjugated diene copolymers and polyolefins.Multifunctional viscosity improvers, which also have dispersant and/orantioxidancy properties are known and may optionally be used in additionto the products of this invention. Such products are described innumerous publications including those mentioned in the Background of theInvention. Each of these publications is hereby expressly incorporatedby reference.

Pour point depressants may be included in the additive concentrates andlubricating oils described herein. Those which may be used are describedin the literature and are well-known to those skilled in the art; seefor example, page 8 of “Lubricant Additives” by C. V. Smalheer and R.Kennedy Smith (Lezius-Hiles Company Publisher, Cleveland, Ohio, 1967).Pour point depressants useful for the purpose of this invention,techniques for their preparation and their use are described in U.S.Pat. Nos. 2,387,501; 2,015,748; 2,655,479; 1,815,022; 2,191,498;2,666,748; 2,721,877; 2,721,878; 3,250,715; and 5,707,943 which areexpressly incorporated herein by reference for their relevantdisclosures.

Anti-foam agents used to reduce or prevent the formation of stable foaminclude silicones or organic polymers. Examples of these and additionalanti-foam compositions are described in “Foam Control Agents”, by HenryT. Kerner (Noyes Data Corporation, 1976), pages 125-162.

Detergents and dispersants may be of the ash-producing or ashless type.The ash-producing detergents are exemplified by oil soluble neutral andbasic salts of alkali or alkaline earth metals with sulfonic acids,carboxylic acids, phenols or organic phosphorus acids characterized by aleast one direct carbon-to-phosphorus linkage.

The term “basic salt” is used to designate metal salts wherein the metalis present in stoichiometrically larger amounts than the organic acidradical. The relative amount of metal present in “basic salts” isfrequently indicated by the expression “metal ratio” (abbreviated MR),which is defined as the number of equivalents of metal present comparedto a “normal”, stoichiometric amount. Thus, for example, a basic saltcontaining twice the amount of metal compared to the stoichiometricamount, has a metal ratio (MR) of 2. Basic salts and techniques forpreparing and using them are well known to those skilled in the art andneed not be discussed in detail here.

Ashless detergents and dispersants are so-called despite the fact that,depending on its constitution, the detergent or dispersant may uponcombustion yield a nonvolatile residue such as boric oxide or phosphoruspentoxide; however, it does not ordinarily contain metal and thereforedoes not yield a metal-containing ash on combustion. Many types areknown in the art, and any of them are suitable for use in the lubricantsof this invention. The following are illustrative:

(1) Reaction products of carboxylic acids (or derivatives thereof)containing at least about 34 and preferably at least about 54 carbonatoms with nitrogen containing compounds such as amine, organic hydroxycompounds such as phenols and alcohols, and/or basic inorganicmaterials. Examples of these “carboxylic dispersants” are described inBritish Patent number 1,306,529 and in many U.S. patents including thefollowing:

3,163,603 3,399,141 3,574,101 3,184,474 3,415,750 3,576,743 3,215,7073,433,744 3,630,904 3,219,666 3,444,170 3,632,510 3,271,310 3,448,0483,632,511 3,272,746 3,448,049 3,697,428 3,281,357 3,451,933 3,725,4413,306,908 3,454,607 4,194,886 3,311,558 3,467,668 4,234,435 3,316,1773,501,405 4,491,527 3,340,281 3,522,179 5,696,060 3,341,542 3,541,0125,696,067 3,346,493 3,541,678 5,779,742 3,351,552 3,542,680 RE 26,4333,381,022 3,567,637

(2) Reaction products of relatively high molecular weight aliphatic oralicyclic halides with amines, preferably polyalkylene polyamines. Thesemay be characterized as “amine dispersants” and examples thereof aredescribed for example, in the following U.S. patents:

3,275,554 3,454,555 3,438,757 3,565,804

(3) Reaction products of alkyl phenols in which the alkyl groupscontains at least about 30 carbon atoms with aldehydes (especiallyformaldehyde) and amines (especially polyalkylene polyamines), which maybe characterized as “Mannich dispersants”. The materials described inthe following U.S. patents are illustrative:

3,413,347 3,725,480 3,697,574 3,726,882 3,725,277

(4) Products obtained by post-treating the carboxylic amine or Mannichdispersants with such reagents as urea, thiourea, carbon disulfide,aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinicanhydrides, nitriles, epoxides, boron compounds, phosphorus compounds orthe like. Exemplary materials of this kind are described in thefollowing U.S. patents:

3,036,003 3,282,955 3,493,520 3,639,242 3,087,936 3,312,619 3,502,6773,649,229 3,200,107 3,366,569 3,513,093 3,649,659 3,216,936 3,367,9433,533,945 3,658,836 3,254,025 3,373,111 3,539,633 3,697,574 3,256,1853,403,102 3,573,010 3,702,757 3,278,550 3,442,808 3,579,450 3,703,5363,280,234 3,455,831 3,591,598 3,704,308 3,281,428 3,455,832 3,600,3723,708,522 4,234,435

(5) Polymers and copolymers of oil-solubilizing monomers such as decylmethacrylate, vinyl decyl ether and high molecular weight olefins withmonomers containing polar substituents, e.g., aminoalkyl acrylates ormethacrylates, acrylamides and poly-(oxyethylene)-substituted acrylates.These may be characterized as “polymeric dispersants” and examplesthereof are disclosed in the following U.S. patents:

3,329,658 3,666,730 3,449,250 3,687,849 3,519,565 3,702,300

The above-noted patents are incorporated herein by reference for theirdisclosures of ashless dispersants.

The above-illustrated other additives may each be present in lubricatingcompositions at a concentration of as little as 0.001% by weight,usually ranging from about 0.01% to about 20% by weight. In mostinstances, they each contribute from about 0.1% to about 10% by weight,more often up to about 5% by weight.

Additive Concentrates

The various additive compositions of this invention described herein canbe added directly to the oil of lubricating viscosity. Preferably,however, they are diluted with a substantially inert, normally liquidorganic diluent such as mineral oil, a synthetic oil such as apolyalphaolefin, naphtha, benzene, toluene or xylene, to form anadditive concentrate. These concentrates comprise from about 0.1 toabout 60% by weight, frequently from about 5% to about 50% by weight,more often from about 5% to about 30% by weight of the copolymers ofthis invention with the balance comprising the substantially inert,normally liquid organic diluent, and may contain, in addition, one ormore other additives known in the art or described hereinabove.

The additive concentrate may comprise from about 3% to about 10% byweight of at least one non-graft polymerized hydrocarbon polymer. Theadditive concentrate may also comprise from about 0.5 to about 5% byweight, based on the total weight of the additive concentrate, of atleast one pour point depressant.

Additive concentrates are prepared by mixing together the desiredcomponents, often at elevated temperatures, usually less than 150° C.,often no more than about 130° C., frequently no more than about 100° C.

The Oil of Lubricating Viscosity

The lubricating compositions and methods of this invention employ an oilof lubricating viscosity, including natural and synthetic oils andmixtures thereof.

Natural oils include animal oils and vegetable oils (e.g., lard oil,castor oil) as well as mineral lubricating oils such as liquid petroleumoils and solvent-treated, acid treated, and/or hydrotreated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types. Oils of lubricating viscosity derived fromcoal or shale are also useful. Synthetic lubricating oils includehydrocarbon oils and halosubstituted hydrocarbon oils such aspolymerized and interpolymerized olefins, etc. and mixtures thereof,alkylbenzenes, polyphenyl, (e.g., biphenyls, terphenyls, alkylatedpolyphenyls, etc.), alkylated diphenyl ethers and alkylated diphenylsulfides and the derivatives, analogs and homologues thereof and thelike.

Alkylene oxide polymers and interpolymers and derivatives thereof wheretheir terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another useful class of known syntheticlubricating oils.

Another suitable class of synthetic lubricating oils that can be usedcomprises the esters of di- and polycarboxylic acids and those made fromC₅ to C₂₀ monocarboxylic acids and polyols and polyolethers.

Other synthetic lubricating oils include liquid esters ofphosphorus-containing acids, polymeric tetrahydrofurans and the like,silicon-based oils such as the polyalkyl-polyaryl-, polyalkoxy-, orpolyaryloxy-siloxane oils and silicate oils.

Unrefined, refined and rerefined oils, either natural or synthetic (aswell as mixtures of two or more of any of these) of the type disclosedhereinabove can be used in the compositions of the present invention.Unrefined oils are those obtained directly from natural or syntheticsources without further purification treatment. Refined oils are similarto the unrefined oils except they have been further treated in one ormore purification steps to improve one or more properties. Rerefinedoils are obtained by processes similar to those used to obtain refinedoils applied to refined oils which have been already used in service.Such rerefined oils often are additionally processed by techniquesdirected to removal of spent additives and oil breakdown products.

Specific examples of the above-described oils of lubricating viscosityare given in Chamberlin, III, U.S. Pat. No. 4,326,972 and EuropeanPatent Publication 107,282, both of which are hereby incorporated byreference for relevant disclosures contained therein.

A basic, brief description of lubricant base oils appears in an articleby D. V. Brock, “Lubrication Engineering”, Volume 43, pages 184-5,March, 1987, which article is expressly incorporated by reference forrelevant disclosures contained therein.

The following examples illustrate lubricating oil compositions of thisinvention. All parts are parts by weight. Amounts are on an oil ordiluent free basis, except for products of Examples set forth hereinwhich amounts are as prepared, including diluent, if any.

EXAMPLES A-B

A master additive concentrate is prepared by mixing together 25.74 partsof a polyisobutylene ({overscore (M)}_(n) ˜1600) substituted succinicanhydride-ethylene polyamines bottoms reaction product, 6.84 parts of azinc salt of mixed methyl amyl-isopropyl dithiophosphate, 4.80 partsdi(nonylphenyl) amine, 6.72 parts calcium overbased (MR ˜2.3) sulfurizedalkyl phenol, 0.98 parts calcium overbased (MR ˜11) alkyl benzenesulfonic acid, 11.88 parts calcium overbased (MR 2.8) alkyl benzenesulfonic acid, 0.08 parts of a kerosene solution of a commercialsilicone antifoam and sufficient mineral oil to make the total 100 partsby weight.

Lubricating oil compositions are prepared by mixing 12.49 parts of themaster additive concentrate, 0.20 parts of a 65% in mineral oilpolymethacrylate pour point depressant and 7.5 parts of the product ofthe Example indicated in the following table into sufficient mineral oil(Exxon SAE 10W-40) to prepare 100 parts of lubricating oil.

TABLE 1 Example A B Product of Example 1 2

EXAMPLE C

A master additive concentrate is prepared by mixing together 12.90 partsof a polyisobutylene ({overscore (M)}_(n) ˜1600) substituted succinicanhydride-ethylene polyamines bottoms reaction product, 11.25 parts of azinc salt of mixed methyl amyl-isopropyl dithiophosphate, 6.49 partscalcium overbased (MR ˜3.5) sulfurized alkyl phenol, 7.48 parts calciumoverbased (MR ˜11) alkyl benzene sulfonic acid, 9.29 parts calciumoverbased (MR 2.8) alkyl benzene sulfonic acid, 4.21 parts calciumoverbased (MR ˜1.1) sulfurized alkyl phenol, 0.32 parts of anS-alkyl-2,5-dimercapto-1,3,4-thiadiazole, 5.38 parts of sulfurizedbutadiene-butyl acrylate Diels-Alder adduct, 0.11 parts of a kerosenesolution of a commercial silicone antifoam and sufficient mineral oil tomake the total 100 parts by weight.

Lubricating oil compositions are prepared by mixing 9.30 parts of themaster additive concentrate, 0.08 parts of a styrene maleate copolymerneutralized with aminopropylmorpholine, and 8 parts of the product ofExample 4 into sufficient mineral oil (Exxon SAE 10W-40) to prepare 100parts of lubricating oil.

EXAMPLES D-E

A master additive concentrate is prepared by mixing together 20.51 partsof a polyisobutylene ({overscore (M)}_(n) ˜1600) substituted succinicanhydride-ethylene polyamines bottoms reaction product, 8.94 parts of azinc salt of mixed methyl amyl-isopropyl dithiophosphate, 5.16 partscalcium overbased (MR ˜3.5) sulfurized alkyl phenol, 5.95 parts calciumoverbased (MR ˜11) alkyl benzene sulfonic acid, 7.38 parts calciumoverbased (MR 2.8) alkyl benzene sulfonic acid, 3.34 parts calciumoverbased (MR ˜1.1) sulfurized alkyl phenol, 0.26 parts of anS-alkyl-2,5-dimercapto-1,3,4-thiadiazole, 4.27 parts of sulfurizedbutadiene-butyl acrylate Diels-Alder adduct, 0.11 parts of a kerosenesolution of a commercial silicone antifoam and sufficient mineral oil tomake the total 100 parts by weight.

Lubricating oil compositions are prepared by mixing 11,70 parts of themaster additive concentrate, 0.08 parts of a styrene maleate copolymerneutralized with aminopropylmorpholine and the indicated amounts of theproduct of the Example indicated in the following table into sufficientmineral oil (Exxon SAE 10W-40) to prepare 100 parts of lubricating oil.

TABLE 2 Example D E Product of Example/(pbw) 4/8.0 6/9.0

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic sites ofother molecules. The products formed thereby, including the productsformed upon employing the composition of the present invention in itsintended use, may not susceptible of easy description. Nevertheless, allsuch modifications and reaction products are included within the scopeof the present invention; the present invention encompasses thecomposition prepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference. Except in the examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about”. Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the upper and lower amount,range, and ratio limits set forth herein may be independently combined.As used herein, the expression “consisting essentially of” permits theinclusion of substances which do not materially affect the basic andnovel characteristics of the composition under consideration.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications that fallwithin the scope of the appended claims.

What is claimed is:
 1. A graft copolymer comprising a hydrocarbonpolymer having graft polymerized thereon at least two nitrogencontaining units, at least one of the nitrogen containing units beingderived from at least one of N-methyl-, N-ethyl-, N,N-dimethyl-,N,N-diethyl-, and N-propyl-(meth)acrylamide, and at least one of thenitrogen containing units being derived from at least one vinylicnitrogen containing heterocyclic compound.
 2. The graft copolymer ofclaim 1 wherein the at least one vinylic nitrogen containingheterocyclic compound comprises an N-vinyl heterocyclic compound.
 3. Thegraft copolymer of claim 2 wherein the N-vinyl heterocyclic compoundcomprises at least one of N-vinyl imidazole and N-vinyl pyrrolidone. 4.The graft copolymer of claim 1 having from about 0.25 to about 5 molesof (meth)acrylamide units per mole of vinylic nitrogen containingheterocyclic units.
 5. The graft copolymer of claim 4 comprising a totalof from about 0.2 to about 5 moles nitrogen containing units per 10,000weight average molecular weight units of hydrocarbon polymer.
 6. Aprocess for preparing graft copolymers comprising simultaneouslygrafting onto a hydrocarbon polymer, under free radical conditions, atleast two nitrogen containing monomers, wherein one of the monomerscomprises at least one of N-methyl-, N-ethyl-, N,N-dimethyl-,N,N-diethyl-, and N-propyl-(meth)acrylamide and one of the monomerscomprises at least one vinylic nitrogen containing heterocycliccompound.
 7. The process of claim 6 wherein the vinylic nitrogencontaining heterocyclic compound is an N-vinyl heterocyclic compound. 8.The process of claim 7 wherein the N-vinyl heterocyclic compoundcomprises at least one of N-vinyl imidazole and N-vinyl pyrrolidone. 9.The process of claim 6 wherein the grafting is conducted in the presenceof a substantially saturated aliphatic hydrocarbon diluent.
 10. Theprocess of claim 9 wherein the diluent is at least one of an oil oflubricating viscosity and a volatile solvent.
 11. The process of claim 6wherein the grafting is conducted in the presence of a free radicalinitiator selected from the group consisting of diazo compounds, peroxycompounds, nitroxyl radicals and high energy radiation.
 12. The processof claim 11 wherein the free radical initiator is selected from thegroup consisting of benzoyl peroxide, t-butyl peroxybenzoate, t-butylperoctoate and t-butyl peroxide.
 13. The process of claim 6 conducted inan extruder.
 14. The process of claim 6 employing from about 0.25 toabout 5 moles methacrylamide monomer per mole of vinylicnitrogen-containing heterocyclic monomer.
 15. The process of claimemploying a total of from about 0.1 to about 5 moles nitrogen containingunits per 10,000 weight average molecular weight units of hydrocarbonpolymer.
 16. A graft copolymer prepared by the process of claim
 6. 17. Amethod for improving the efficiency of the free radical initiatedgrafting of vinylic nitrogen containing heterocyclic monomers ontohydrocarbon polymers said method comprising simultaneously co-graftingwith a mixture of the vinylic nitrogen containing heterocyclic monomerand at least one of N-methyl-, N-ethyl-, N,N-dimethyl-, N,N-diethyl-,and N-propyl-(meth)acrylamide.
 18. The method of claim 17 wherein thegrafting is conducted in the presence of a substantially saturatedhydrocarbon diluent.
 19. The method of claim 17 wherein the vinylicnitrogen containing heterocyclic monomer is N-vinyl imidazole.
 20. Anadditive concentrate comprising from about 5% to about 50% by weight ofthe graft copolymer of claim 1 and from about 50% to about 95% by weightof a normally liquid, substantially inert organic diluent.
 21. Anadditive concentrate comprising from about 5% to about 50% by weight ofthe graft copolymer of claim 16 and from about 50% to about 95% byweight of a normally liquid, substantially inert organic diluent. 22.The additive concentrate of claim 20 further comprising from about 3% toabout 10% by weight of at least one non-graft polymerized hydrocarbonpolymer.
 23. The additive concentrate of claim 20 comprising from 0.5%to about 5% by weight, based on the total weight of the additiveconcentrate, of at least one pour point depressant.
 24. A lubricatingoil composition comprising a major amount of an oil of lubricatingviscosity and a minor, viscosity improving and dispersant amount of thegraft copolymer of claim
 1. 25. A lubricating oil composition comprisinga major amount of an oil of lubricating viscosity and a minor, viscosityimproving and dispersant amount of the graft copolymer of claim
 16. 26.A method for improving the viscometrics and dispersancy characteristicsof a lubricating oil composition, said method comprising incorporatingtherein a minor, viscosity improving and dispersant amount of the graftcopolymer of claim
 1. 27. A method for improving the viscometrics anddispersancy characteristics of a lubricating oil composition, saidmethod comprising the incorporating there a minor, viscosity improvingand dispersant amount of the graft copolymer of claim 16.